<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:complexType name="person_type">
        <xs:sequence>
            <xs:element name="name" type="xs:string"/>
            <xs:element name="email" type="xs:string"/>
        </xs:sequence>
        <xs:attribute name="gender">
            <xs:simpleType>
                <xs:restriction base="xs:string">
                    <xs:enumeration value="male"/>
                    <xs:enumeration value="female"/>
                </xs:restriction>
            </xs:simpleType>
        </xs:attribute>
    </xs:complexType>
    
    <xs:element name="person" type="person_type"/>
    
    <xs:complexType name="directory_type">
        <xs:sequence>
            <xs:element ref="person" minOccurs="0" 
                                     maxOccurs="unbounded"/>
        </xs:sequence>
    </xs:complexType>
    
    <xs:element name="directory" type="directory_type"/>
</xs:schema>
